docs: def to_json(self):
          """
          Returns a json-compatible object from the model that can be saved using the json module.
          Variables, constraints and objective contained in the model will be saved. Configurations
          will not be saved.
  
          Example
          --------
          >>> import json
          >>> with open("path_to_file.json", "w") as outfile:
          >>>     json.dump(model.to_json(), outfile)
          """
          json_obj = {
              "name": self.name,
              "variables": [var.to_json() for var in self.variables],
              "constraints": [const.to_json() for const in self.constraints],
              "objective": self.objective.to_json()
          }
          return json_obj